1. Field of the Invention
The present disclosure relates to an electrophotographic image forming apparatus and a process cartridge that can detachably attach to an electrophotographic image forming apparatus.
2. Description of the Related Art
Here, an electrophotographic image forming apparatus (hereinafter, also referred simply to as an “image forming apparatus”) is an image forming apparatus that forms an image on a recording medium by using an electrophotographic image forming method. Examples of the image forming apparatus include an electrophotographic copying machine, an electrophotographic printer (for example, a laser beam printer, an light-emitting diode (LED) printer, or the like), a facsimile apparatus, and a multifunction peripheral (multifunction printer) thereof, and the like.
In addition, the process cartridge refers to a device in which at least a developing unit as a process unit and an electrophotographic photosensitive drum are integrally configured as a process cartridge to be detectably attached to an image forming main assembly.
Conventionally, in image forming apparatuses using an electrophotographic image forming process, an electrophotographic photosensitive member and a process unit that acts on the electrophotographic photosensitive member are integrally configured as a process cartridge.
Thus, a process cartridge type is employed which enables the process cartridge to be detachably attached to the image forming main assembly. According to the process cartridge type, the maintenance of an apparatus is performed not by a service staff but by a user, whereby the operability can be markedly improved.
For the process cartridge, a contact developing method is adopted in which developing is performed in a state in which a development roller is brought into contact with a photosensitive drum. According to the method, to maintain predetermined pressure between the development roller and the photosensitive drum, which are in the process of forming an image, a state is formed in which the development roller including an elastic layer is pressed to the photosensitive drum. However, when such a state is continued for a long time, the elastic layer of the development roller may be deformed to affect an image. Accordingly, for example, Japanese Patent Application Laid-Open No. 2008-170950 discuses a configuration in which the development roller is separated from the photosensitive drum by using a separation member at the time of no image formation.
In addition, for a charging roller as a unit that charges the photosensitive drum, a contact charging method is widely used in which the charging roller is brought into contact with the photosensitive drum. Also in such a case, since it is necessary to reliably bring the charging roller into contact with the surface of the photosensitive drum, the charging roller is brought into contact with the surface of the photosensitive drum at predetermined pressure. Thus, when such a state is continued for a long time, an elastic layer of the charging roller may be deformed to affect an image. Accordingly, for example, Japanese Patent Application Laid-Open No. 2002-6722 and Japanese Patent Application Laid-Open No. 2008-170965 discuss a configuration in which the charging roller is separated from the photosensitive drum by using a separation member at the time of no image formation.
Furthermore, a photosensitive member unit includes a cleaning blade that is used for removing toner adhering to the photosensitive drum after transfer. To scrape off the toner adhering to the photosensitive drum, the cleaning blade is in the state of being pressed to the photosensitive drum. Thus, for example, Japanese Patent Application Laid-Open No. 2001-305925 discusses a configuration in which the pressing force of the cleaning blade toward the photosensitive drum at a time when the process cartridge is separated is reduced.